The general field of the invention is air conditioning. As is well known, it is common to provide a main partition in an air conditioner with the evaporator being on the room side of the partition and the condenser and compressor being on the outside. In one mode of operation, the room air is recirculated through the evaporator for cooling. In another mode of operation, it is desirable to introduce fresh air from the outside to mix with the recirculating air. For certain specified applications such as, for example, nursing homes, federal regulations require that at least 20 percent of the rated evaporator air be fresh air.
In most prior art designs, the evaporator blower wheel brings in the fresh air through one or more openings in the main partition. These openings have been located in areas of convenience and are accordingly only marginally effective at drawing in fresh air. More specifically, the evaporator blower wheel motor is typically mounted to the outside of the main partition and its shaft extends through a hole in the partition to the evaporator blower wheel which is enclosed in a scroll. When fresh air is desired, a vent door in the main partition is opened and a path is provided for air to flow by evaporator blower wheel suction through the main partition to a first 90.degree. bend and then to a second 90.degree. bend where it mixes with the recirculation air as it enters the front of the evaporator blower wheel through the recirculation air orifice. With such a configuration, the fresh air flow rate may typically be in the range from a few cubic feet per minute (CFM) to 10 or 20 CFM for an air conditioner having a evaporator rating of 270 CFM. This is substantially below the federal regulation for specified applications. Further, because the flow of fresh air through the fresh air vent is drawn by a relatively slight negative pressure created at the vent door by the evaporator blower wheel, the flow rate can be substantially influenced by other factors such as the condenser fan. More specifically, if the condenser fan on the back side of the partition is on at the same time that the vent door is open, some of the air which would otherwise be drawn through the main partition as fresh air could be drawn by the condenser fan and passed through the condenser to the outside.
In one prior art air conditioner, the amount of fresh air passing into the system through the main partition is increased by positioning the door opening through the partition at a positive static air location as created by the condenser fan. In other words, the fresh air flow rate is increased because both the evaporator blower wheel and the condenser fan work together. This configuration, however, requires that the condenser fan and the evaporator blower wheel be operated simultaneously.